0262-821X/08 $15.00 2008 The Micropalaeontological Society
Journal of Micropalaeontology, 27: 5–12.
Acarinina multicamerata n. sp. (Foraminifera): a new marker for the Paleocene–Eocene thermal
maximum
ELISA GUASTI1 & ROBERT P. SPEIJER2
1
Department of Geoscience, Bremen University, PO Box 330 440, Bremen, Germany (Current address: Geobiology team – TNO, Princetonlaan,
6, 3584 CB Utrecht, The Netherlands, e-mail: elisa.guasti@tno.nl)
2
Department of Geography and Geology, KU Leuven, Celestijnenlaan 200E, 3001 Leuven, Belgium (e-mail: Robert.Speijer@geo.kuleuven.be)
ABSTRACT – During the Paleocene–Eocene thermal maximum (PETM), low to mid-latitude planktic
foraminiferal assemblages were characterized by blooms of the surface-dwelling Acarinina. Among this
group a new ‘excursion taxon’ is identified, Acarinina multicamerata n. sp. Previously, this taxon was
lumped together with Acarinina sibaiyaensis El-Naggar. Considering that A. sibaiyaensis already occurred
prior to the hyperthermal event, both in open ocean and ocean margin deposits, it is proposed that these
taxa are differentiated in order to avoid taxonomic and biostratigraphic ambiguities. Acarinina multicamerata n. sp. occurred exclusively during the PETM, hence this taxon represents an excellent biostratigraphic marker of the PETM, while its common occurrence in various marine settings makes it an excellent
marker of Subzone P5b or its new equivalent zone E1. J. Micropalaeontol. 27(1): 5–12, May 2008.
KEYWORDS: planktic foraminifera, Acarinina, excursion taxa, Paleocene, PETM
INTRODUCTION
The Paleocene–Eocene thermal maximum (PETM) represents a
period of extreme global warmth (Zachos et al., 1993), associated with various biotic turnovers on land and in the sea.
Among the latter is an evolutionary rejuvenation in planktic
foraminifera, leading to short-lived species of Acarinina and
Morozovella (Kelly et al., 1996). During the PETM, planktic
foraminiferal assemblages in open-marine environments worldwide are dominated strongly by Acarinina. Both in open ocean
ODP sites and in the marginal Tethys, a number of authors have
described the occurrence of new planktic foraminifera taxa,
called ‘excursion’ taxa, at the PETM; these include Acarinina
sibaiyaensis, A. africana and Morozovella allisonensis. These are
generally thought to have evolved during the early part of the
PETM (Kelly et al., 1996, 1998; Bolle et al., 2000; Berggren &
Ouda, 2003; Ouda et al., 2003). Observations on Egyptian
successions, however, show that A. sibaiyaensis and A. africana
(=M. africana) indeed bloom during the PETM, but had already
evolved prior to this event (Speijer et al., 2000; Guasti & Speijer,
2007), confirming the early observations of El-Naggar (1966),
the author who erected these taxa.
This study examined material from upper Paleocene–lower
Eocene successions in Egypt (Dababiya, Gebel Duwi, Gebel
Aweina, Gebel Qreiya and Wadi Nukhl) and Jordan (Gebel
Qurtassyat) (Figs 1, 2) in order to investigate the occurrence and
taxonomy of excursion taxa. It was found that there are some
ambiguities in the taxonomy of the PETM excursion taxa. In
this paper, the longer-ranging species A. sibaiyaensis is differentiated from a multi-chambered Acarinina species, which only
occurred during the PETM. The latter is defined as A. multicamerata n. sp. In addition. environmental scanning electron microscope (ESEM) images of the holotypes of A. sibaiyaensis and A.
africana are provided. Images of these holotypes, as well as the
holotype and paratype of A. multicamerata n. sp., were taken
at the Natural History Museum of London (UK), using an
ESEM with variable pressure (LEO 1455 VP), which allowed
photography of specimens in a mounting slide without coating.
ACARININA SIBAIYAENSIS
The holotypes of Acarinina sibaiyaensis and A. africana were
described originally by El-Naggar (1966) as Globorotalia sibaiyaensis and Globorotalia africana, respectively (Pl. 1). He observed
these species in the upper Paleocene, at Gebel Aweina in the Nile
Valley, Egypt. In the original description, Globorotalia sibaiyaensis was described as a compressed small, globular species, in
which the last whorl is composed of 5.5 chambers, having a long
narrow aperture. El-Naggar (1966) suggested that this taxon
may have evolved from G. perclara Loeblich & Tappan (1957).
Our observations uncovered a number of problems on the
evolution, morphology and range of A. sibaiyaensis in the
literature. For instance, Kelly et al. (1998) provided a very
Fig. 1. Location map of the studied profiles (black dots). The normal
dashed lines indicate the estimated palaeobathymetry based on Speijer &
Van der Zwaan (1994).
5
E. Guasti & R. P. Speijer
Fig. 2. Stratigraphic correlation of the localities arranged along a transect from the deeper localities on the left to the shallowest ones on the right
(roughly N–S orientation). Gebel Aweina has been vertically exaggerated. Modified after Guasti & Speijer (2007).
different description of A. sibaiyaensis compared with the holotype description. These authors considered A. sibaiyaensis as a
globular flat species with 6–9 chambers, which in their view
seemed to evolve from Acarinina soldadoensis Brönniman
(1952). To support this evolutionary linkage, Kelly et al. (1998)
showed a morphological sequence from A. soldadoensis to A.
sibaiyaensis (fig. 9, p. 150). In the current authors’ view, the
specimen presented as A. soldadoensis (specimen ‘A’) in this cline
seems already very close to A. sibaiyaensis sensu El-Naggar
(1966) and quite different from A. soldadoensis. Acarinina soldadoensis is composed of 4–5 chambers gradually increasing in
size, distinctively elongated in the direction of the coiling axis of
the test; at the umbilical side the chambers tend to become
pointed. The sutures of the spiral side are oblique, giving the
impression of overlapping chambers (Olsson et al., 1999). These
diagnostic features are missing in the specimens considered by
Kelly et al. (1998) as A. soldadoensis. At the other end of the
6
cline, the multi-chambered (6–9 chambers) forms of A. sibaiyaensis sensu Kelly et al. (1998) are readily distinguished from A.
sibaiyaensis El-Naggar (1966), although the taxa may be linked
phylogenetically. Moreover, A. sibaiyaensis should not be confused with Acarinina esnaensis LeRoy (1953), which also occurs
in the Esna Formation during the Paleocene. Acarinina esnaensis
differs from A. sibaiyaensis most notably in having a quadrate
outline and only 4–4.5 subovate to subspherical chambers in the
last whorl.
Arenillas et al. (2004) also found specimens of the multichambered form of A. sibaiyaensis within the PETM horizons.
These authors suggested that Acarinina strabocella Loeblich &
Tappan (1957) could have been the ancestor of A. sibaiyaensis,
although this would be in conflict with observations by various
other authors, who recorded the highest occurrence of A.
strabocella in lower Zone P4 (Lu et al., 1998; Olsson et al.,
1999).
A. multicamerata n. sp., a new PETM marker
Explanation of Plate 1.
figs 1–3. Acarinina sibaiyaensis (El-Naggar) 1966, holotype: 1, umbilical view; 2, side view; 3, spiral view. Collection number P.45628, the Natural
History Museum, London (NHM). figs 4–6. Acarinina africana (El-Naggar) 1966, holotype: 4, umbilical view; 5, side view; 6, spiral view. Collection
number P.45593, the NHM. (figs 1–6 all from sample S. 50, 8 m above the base of the Esna Formation (‘upper Owaina Shale’) at Gebel Aweina
(‘Owaina’), Nile Valley, Egypt.) figs 7–11. Acarinina multicamerata n. sp., holotype: 7, umbilical view; 8, side view; 9, spiral view; 10, 11, details of
the wall texture (scale bar 10 µm). From sample BI3+8–12, 15 m above the base of the Esna Formation at Gebel Duwi, Red Sea Coast, Egypt.
Collection number PF 67590, the NHM. Scale bar represents 100 µm, unless otherwise specified.
7
E. Guasti & R. P. Speijer
Berggren et al. (2006) re-described A. sibaiyaensis based on
material from a couple of ODP cores, most notably from Bass
River, New Jersey. In their description these authors considerably widened the concept of A. sibaiyaensis by including specimens with much more numerous chambers to a whorl. In
contrast, El-Naggar’s holotype is comprised of 5.5 chambers in
the last whorl, whereas one of his paratypes (depicted here in Pl.
2) has only 4 chambers in the last whorl. Apparently the
specimens of El-Naggar came from an upper Paleocene population with relatively few chambers to a whorl. This is the kind
of variation that was also observed for A. sibaiyaensis in upper
Paleocene deposits in Egypt. Berggren et al. (2006) studied
lowermost Eocene populations of flat-spired Acarinina and
proposed intergradations between typical specimens of A.
sibaiyaensis conformable with El-Naggar’s concept and a variety
with more numerous chambers in the last whorl. The latter
variety has been observed associated with the PETM also by
various other authors (i.e. Kelly et al., 1996, 1998; Pardo et al.,
1999; Arenillas et al., 2004) and was also identified as A.
sibaiyaensis.
In the current authors’ view the variety with 6–9 chambers in
the last whorl qualifies as a new species, Acarinina multicamerata
n. sp., described below. The concept of this taxon includes
specimens 7, and 9–14 of plate 9.21 of Berggren et al. (2006).
Besides the larger number of chambers in the last whorl, these
specimens have a more rounded outline and a wider umbilicus
compared with A. sibaiyaensis. All other specimens depicted by
Berggren et al. (2006) seem to represent transitional forms
between A. sibaiyaensis and A. multicamerata in having features
typical of both these specimens. This reinforces the idea that
during the PETM diversification of muricate taxa (Acarinina,
Morozovella) occurred (Kelly et al., 1998) and that a variety of
flat-spired Acarinina bloomed. Before the PETM, morphological variability was subdued and only the typical A. sibaiyaensis
occurred sporadically. During the PETM A. multicamerata
diverged from A. sibaiyaensis.
Lumping these two morphologically distinct taxa into one
species would also lead to a loss of stratigraphic resolution.
Acarinina multicamerata has been observed exclusively within
PETM beds. A. sibaiyaensis and A. africana (by some considered
as Morozovella because of the slightly keeled last chamber(s))
already appeared during the late Paleocene as indicated by the
data of El-Naggar (1966). He recorded these taxa from the
topmost metres of the upper Paleocene ‘Middle Owaina Chalk’
(=Tarawan Formation) and the lowermost 14 m of the overlying
‘Upper Owaina Shale’ (=Esna Formation) in the Aweina section
(El-Naggar, 1966, fig. 18). This corresponds to a range from
Zone P4 to the lower part of Zone P5 (Subzone P5a and possibly
slightly higher) of Berggren et al. (1995), when compared to
more recent studies on this section (Speijer et al., 1995, 2000;
Ouda et al., 2003). Observations have confirmed the occurrence
of A. africana and A. sibaiyaensis in Aweina at least 40 cm below
the P/E boundary (Pl. 2, Table 1). El-Naggar’s observations
lower in the Aweina section cannot be confirmed, because
planktic taxa in samples from below the PETM (upper Tarawan
Fm. and lower Esna Fm) are poor in number and preservation
(Speijer & Schmitz, 1998). Ouda et al. (2003) also observed these
taxa below the unconformity at the basis of the ‘calcarenitic
bed’, which, according to earlier studies (Speijer et al., 1995,
8
2000; Schmitz et al., 1997), marks the P/E boundary. In contrast
to the opinion of Ouda et al. (2003), who considered this interval
an early part of the PETM, the beds below the ‘calcarenitic
bed’ belong to the uppermost Paleocene as indicated by the
position of the carbon isotopic excursion coinciding with the
unconformity (Speijer et al., 1995; Guasti & Speijer, 2007).
This view is corroborated further by recent preliminary
observations of pre-PETM occurrences of these taxa in ODP
Hole 1220, equatorial Pacific (Norris & Nunes, 2004). In conclusion, the widely adopted reference to A. africana and A.
sibaiyaensis as ‘excursion taxa’ is erroneous. Morozovella allisonensis and Acarinina multicamerata n. sp. are thus far the only
planktic ‘excursion taxa’ exclusively observed in PETM beds.
SYSTEMATIC DESCRIPTIONS
Suborder Globigerinida Blow, 1979
Superfamily Globigerinacea Carpenter, Parker & Jones, 1862
Family Truncorotaloididae Loeblich & Tappan, 1961
Subfamily Truncorotaloidinae Loeblich & Tappan, 1961
Genus Acarinina Subbotina, 1953
Acarinina multicamerata n. sp.
(Pl. 1, figs 7–11; Pl. 2, figs 4–15)
1996 A. sibaiyaensis (El-Naggar); Kelly et al.: 424, figs 2–1a to
2-1b.
1998 A. sibaiyaensis (El-Naggar); Kelly et al.: 145, fig. 5c; 150
fig. 9D–E (hypotype).
1999 A. sibaiyaensis (El-Naggar); Pardo et al.: 44, figs 19–20.
2006 A. sibaiyaensis (El-Naggar); Berggren et al.: chapter 9,
pl. 9.21, figs 7, 9–14.
Non Globorotalia sibaiyaensis El Naggar (1966): 235, pl. 23,
figs 6a–c (holotype).
Type species. Acarinina multicamerata n. sp.
Derivation of name. The species name multicamerata derives
from the numerous chambers in the final whorl, which characterize this taxon.
Diagnosis. Test coiled in a low trochospire, containing 6–9
chambers in the final whorl. The chambers are globular and
gradually increase in size. Dorsally flattened tests with rounded
and lobate peripheral margin. The umbilicus is generally deep.
The sutures are radial on both sides and strongly depressed,
particularly on the ventral side. The aperture is an interiomarginal, extraumbilical–umbilical low elongate arch extending
from the umbilicus to the periphery. Wall texture: non spinose,
muricate.
Locality and horizon. Gebel Duwi, 26(05# N and 34(07# E,
12 km east of the town of Quseir (Red Sea Coast, Egypt).
Sample BI3+8–12, collected from the 30 cm thick pink
coprolite-rich marl bed, 15 m above the base of the Esna
Formation. This bed appears to be an equivalent to Dababiya
Quarry bed 3 in the GSSP section of Dababiya (Dupuis et al.,
2003).
Age. Base Ypresian.
A. multicamerata n. sp., a new PETM marker
Explanation of Plate 2.
figs 1–3. Acarinina sibaiyaensis (El Naggar) 1966, paratype: 1, umbilical view; 2, side view; 3, spiral view. Collection number P.45629, the NHM (scale
bar 75 µm). figs 4–6. Acarinina multicamerata n. sp., paratype 1: 4, umbilical view; 5, side view; 6, spiral view. Collection number PF 67591, the
NHM. figs 7–9. Acarinina multicamerata n. sp., paratype 2: 7, umbilical view; 8, side view; 9, spiral view. Collection number PF 67592, the NHM.
figs 10–12. Acarinina multicamerata n. sp., paratype 3: 10, umbilical view; 11, side view; 12, spiral view. Collection number PF 67593, the NHM.
figs 13–15. Acarinina multicamerata n. sp.: 13, from sample BI3+12–14 in the Esna Formation at Gebel Duwi, Red Sea Coast, Egypt; 14, 15 and figs
4–12 all from sample BI3+8–12, 15 m above the base of the Esna Formation at Gebel Duwi, Red Sea Coast, Egypt. fig. 16. Acarinina africana: from
sample O95-30-40 in the Esna Formation at Gebel Aweina, Egypt (scale bar 50 µm). Scale bar represents 100 µm unless otherwise specified.
9
E. Guasti & R. P. Speijer
Samples
Gebel Qurtassyat
JQ 66
JQ 65
JQ 64
hiatus
JQ 63
Gebel Dababyia
DBH 4.5
DBH 4
DBH 3.75
DBH 3.25
DBH 3.12
DBH 3
DBH 2.72
DBH 2.52
DBH 2.3
DBH 2.25
DBH 2.17
DBH 1.8
DBH 2
DBH 1.65
DBH 1.6
DBH 1.57
DBH 1.56
Wadi Nukhl
S 1374
S 1373
S 1372
S 1371
S 1370
Gebel Aweina
32–35
21–25
17–21
15–18
9–12
7–9
6–7
2–6
0–2 (bur)
0–2
0–2
2–6
6–10
10–13
13–15
15–20
20–25
25–30
30–40
Gebel Qreiya
271185/22
271185/23
271185/24
271185/25
271185/26
271185/28
Gebel Duwi
1030
14–16
8–12
1029
0–3
1028
1027
1026
1025
Depth (m)
13C (whole rock)
62.5
61.9
61.1
0.27
1.92
2.19
60.5
0.18
4.5
4
3.75
3.25
3.12
3
2.72
2.52
2.3
2
2.25
1.8
2
1.65
1.6
1.57
1.56
6.8
6.55
6.3
6.05
5.8
25.05
25.59
25.44
26.39
27.18 dissolution
27.33
dissolution
27.14
26.98 dissolution
A. multicamerata
A. sibaiyaensis
X
X
60.8 m
X
X
X
X
X
X
X
X
X
X
26.68
25.82
26.06
25.38
25.61
24.39
0.1
0.696
1.389
1.756
0.776
133.5
123
119
116.5
110.5
108
106.5
104
101
101
99
96
92
88.5
86
82.5
77.5
72.5
65
0.21
16.4
13.8
11.8
9.4
8.4
5.4
0.25
0.23
0.81
1.49
2.46
1.12
60
15
10
10
1.5
40
90
140
190
2.28
2.59
2.81
2.73
3.56
1.33
0.12
0.3
0.23
P/E boundary
1.57 m
X
X
X
6.2 m
0.34
0.45
7 cm (omission surface)
1.15
1.05
1.1
X
1.05
X
X
X
X
8m
X
X
X
X
X
X
X
X
0 cm
X
The data were published previously in Guasti & Speijer (2007), Dupui et al. (2003), Speijer et al. (1997, 2000) and Schmitz et al. (1996).
Table 1. Samples list and depths across the Paleocene/Eocene boundary for each locality, together with the 13C, the occurrences of A. sibaiyaensis
and A. multicamerata and the position of the Paleocene/Eocene boundary.
10
A. multicamerata n. sp., a new PETM marker
Distribution. Tropical-subtropical latitudes.
Dimensions. Maximum diameter: 253 µm; minimum diameter:
218 µm; thickness: 118 µm.
Stratigraphic range. Restricted to the Paleocene–Eocene thermal
maximum (DQB2–DQB4 in the GSSP section of Dababiya), in
the middle part of Zone P5 sensu Berggren et al. (1995) or Zone
E1 of Berggren & Pearson (2005). The range of Acarinina
multicamerata replaces M. allisonensis as the marker species of
Subzone P5b. The common occurrence of this species makes it a
more suitable subzonal marker than the occasionally rare M.
allisonensis, as proposed by Speijer et al. (2000). It would also be
a better replacement for A. sibaiyaensis as the zonal marker of
Zone E1 in the scheme of Berggren & Pearson (2005). As
pointed out above, A. sibaiyaensis is not restricted to the
lowermost Eocene and, consequently, E1 as defined now would
span the uppermost Paleocene to lowermost Eocene, at least at
Aweina and Duwi and, according to the data of Norris & Nunes
(2004), also at ODP Site 1220 in the central Pacific
Remarks. Acarinina multicamerata differs from A. sibaiyaensis in
several features. A. multicamerata has a larger number of
chambers per whorl and the outline is overall more rounded.
The chambers increase more gradually in size compared to A.
sibaiyaensis. In some specimens, the wall texture of A. multicamerata is dominated by the large pores, instead of being
covered with spiky pustules. The umbilicus is generally narrower
in A. sibaiyaensis, resulting in a more tightly coiled test compared to A. multicamerata. The number of chambers (6), a
rounded outline and a wider umbilicus are also evident in the
specimens of Berggren et al. (2006, pl. 9.21, figs 9–14), suggesting the attribution of these specimens to A. multicamerata. All
the other specimens seem to represent a transitional form
between A. sibaiyaensis and A. multicamerata.
Origin of the species. El-Naggar suggested that A. sibaiyaensis
evolved from G. perclara Loeblich & Tappan (1957), which
already occurred in the Danian, but it has been reinterpreted as
benthic foraminifera by Liu et al. (1998). Instead, Kelly et al.
(1998) suggested that A. sibaiyaensis (=A. multicamerata)
evolved from A. soldadoensis. Berggren et al. (2006) proposed
Acarinina esnehensis as the ancestor of A. sibaiyaensis. The
possibility that A. sibaiyaensis could derive from A. esnehensis is
not excluded, although the morphology is distinctively different.
It is suggested that A. multicamerata is derived from A.
sibaiyaensis, as evidenced in the similar wall-textures and in the
occurrence of transitional specimens. A. multicamerata diverged
from the parent species to adapt to different environmental
conditions.
Repository. The holotype (PF 67590) and three paratypes (PF
67591, PF 67592, PF 67593) are deposited at the Natural
History Museum of London (UK).
CONCLUSION
The studied material indicates that Acarinina multicamerata is
the only known Acarinina species occuring exclusively within the
PETM beds. It can be distinguished easily from its precursor
species A. sibaiyaensis, with which it has been confused previously. Hence, it is proposed that A. multicamerata n. sp. and
M. allisonensis are presently the only true PETM excursion taxa
among planktic foraminifera. Because of the exclusive and
common occurrence within the PETM, A. multicamerata acts as
an excellent marker of Subzone P5b or E1, replacing the less
common M. allisonensis or the longer-ranging A. sibaiyaensis.
ACKNOWLEDGEMENTS
The authors warmly thank Drs John Whittaker, Andy
Henderson and Ben Williamson (all of the Natural Museum,
London) for providing photographic material of the holotypes
and paratypes of Acarinina multicamerata, A. sibaiyaensis and
A. africana. Thoughtful suggestions from Clay Kelly, an anonymous reviewer and the editor John Gregory (PetroStrat Ltd)
improved the manuscript greatly.
Manuscript received 6 October 2005
Manuscript accepted 29 May 2007
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